The downscaling of product sizes is one of the most important considerations in the development of electronic products. For example, the acceptability, and therefore success, of many products, such as laptop computers, hand-held computers, portable printers, and a myriad of other hand-held consumer electronic products, is directly dependent upon their relatively miniature size and light weight.
In products that require printing capabilities, perhaps the most significant limitation to downsizing is the printing mechanism, even though relatively small sized printing technologies exist, such as thermal, electro-sensitive, impact, inkjet, pen based, xerographic, magnetic, and thermal-transfer. Unfortunately, the reliability and speed of systems incorporating such technologies diminish as they are downscaled to the size of handheld electronic products. Furthermore, the low quality of the print from certain technologies, such as thermal and electro-sensitive printing, presents a significant drawback. These technologies are also unattractive because of their requirement for special paper.
Many other considerations are relevant to the success of miniature printing in hand-held electronic products. For example, hand-held electronic products incorporating printing systems demand very low power and very light weight, in addition to the already mentioned need for highly reliable quality printing. For instance, impact, x-y pen based, xerographic, or magnetic printing technologies, can be made to a miniature scale, but draw large amounts of current requiring the use of C size, D size or rechargeable batteries. Also, their size and weight are prohibitive due to the nature of hand-held electronic products. Thermal transfer, though much smaller, still demands high current, therefore requiring larger batteries, thus increasing both size and weight.
Another requirement for acceptability is ease of replacement of various parts. For example, replaceable ink cartridges or ribbons must be easily accessible and user replaceable. Also, these ink cartridges or ribbons must be designed for easy handling and not have requirements for special tools, and must not soil the user during replacement.
A particular application for miniature printing mechanisms in which these demands must be met is that of electronic checkbooks. With an electronic checkbook, transactional data is entered into the unit and checks are printed with the transactional data, including the amount of purchase, payee, date, and other data, such as a memorandum. The check is then ejected for the signature of the check writer. An electronic checkbook also keeps an electronic record, or register, of all transactions made. To date, no electronic checkbook exists that includes a printing mechanism capable of meeting the requirements of very low power, high quality, high reliability, easy maintenance and miniature size.
An example of a printing mechanism used in an electronic checkbook is disclosed in U.S. Pat. No. 4,623,965 issued Nov. 18, 1986 to Donald K. Wing. The printing mechanism disclosed in the Wing patent discloses a print mechanism using an ink pad and pen driven by three motors for writing information on a check. The use of these three motors and the spans required in that patent require relatively significant amounts of power to operate, and the unit is relatively large. Furthermore, the ink pad and pen disclosed provide relatively low quality printing as opposed to other technologies, such as inkjet printing. Moreover, the reliability of the printing mechanism disclosed in Wing is diminished as there is no stated feedback mechanism for determining the exact location of the printing stylus.
Therefore, a need has arisen for a printing mechanism for use in hand-held electronic products, such as an electronic checkbook, that operates on very low power with high printing reliability and high print quality. Furthermore, a need has arisen for an electronic checkbook with such a printer.